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Analogy to a wormhole in a curved 2-D space (see Embedding Diagram)
An artist's impression of a wormhole from an observer's perspective, crossing the event horizon of a Schwarzschild wormhole, which is similar to a Schwarzschild black hole, but with the singularity replaced, by an unstable path to a white hole, in another universe. The observer originates from the right, and another universe becomes visible in the center of the wormhole’s shadow once the horizon is crossed; however, this new region is unreachable in the case of a Schwarzschild wormhole, as the bridge, between the black hole and the white hole, always collapses before the observer has time to cross it. See White Holes and Wormholes for a technical discussion and animation of what an observer sees when falling into a Schwarzschild wormhole.

In physics and fiction, a wormhole is a hypothetical topological feature of spacetime that would be, fundamentally, a "shortcut" through spacetime. Although they are very popular in science fiction, there is no actual evidence that they exist. For a simple visual explanation of a wormhole, consider spacetime visualized as a two-dimensional (2-D) surface (see illustration, right). If this surface is "folded" along a (non-existent) third dimension, it allows one to picture a wormhole "bridge". (Please note, though, that this image is merely a visualization displayed to convey an essentially unimaginable structure existing in 4 or more dimensions.) A wormhole is, in theory, much like a tunnel with two ends each in separate points in space-time.

There is no observational evidence for wormholes, and, although wormholes are valid solutions in general relativity, this is only true if exotic matter can be used to stabilize them. Even if the wormhole is stabilized, the slightest fluctuation in space would collapse it. If such exotic matter (that is, matter with negative mass) does not exist, all wormhole-containing solutions to Einstein's field equations are vacuum solutions, which require an impossible vacuum, free of all matter and energy. There is no evidence or experimental suggestion that wormholes do exist, except as predictions of certain (exotic) physical models. Wormholes allowed by current physical theories might arise spontaneously, but would vanish nearly instantaneously, and would likely be undetectable.

The American theoretical physicist John Archibald Wheeler coined the term wormhole in 1957; however, in 1921, the German mathematician Hermann Weyl already had proposed the wormhole theory, in connection with mass analysis of electromagnetic field energy.[1]

This analysis forces one to consider situations...where there is a net flux of lines of force, through what topologists would call "a handle" of the multiply-connected space, and what physicists might perhaps be excused for more vividly terming a "wormhole".
John Wheeler in Annals of Physics

Contents

Definition

The basic notion of an intra-universe wormhole is that it is a compact region of spacetime whose boundary is topologically trivial but whose interior is not simply connected. Formalizing this idea leads to definitions such as the following, taken from Matt Visser's Lorentzian Wormholes.

If a Minkowski spacetime contains a compact region Ω, and if the topology of Ω is of the form Ω ~ R x Σ, where Σ is a three-manifold of the nontrivial topology, whose boundary has topology of the form dΣ ~ S2, and if, furthermore, the hypersurfaces Σ are all spacelike, then the region Ω contains a quasipermanent intra-universe wormhole.

Characterizing inter-universe wormholes is more difficult. For example, one can imagine a 'baby' universe connected to its 'parent' by a narrow 'umbilicus'. One might like to regard the umbilicus as the throat of a wormhole, but the spacetime is simply connected.

Schwarzschild wormholes

Embedded diagram of a Schwarzschild wormhole.

Lorentzian wormholes known as Schwarzschild wormholes or Einstein-Rosen bridges are bridges between areas of space that can be modeled as vacuum solutions to the Einstein field equations by combining models of a black hole and a white hole. This solution was discovered by Albert Einstein and his colleague Nathan Rosen, who first published the result in 1935. However, in 1962 John A. Wheeler and Robert W. Fuller published a paper showing that this type of wormhole is unstable, and that it will pinch off instantly as soon as it forms, preventing even light from making it through.

Before the stability problems of Schwarzschild wormholes were apparent, it was proposed that quasars were white holes forming the ends of wormholes of this type.[citation needed]

While Schwarzschild wormholes are not traversable, their existence inspired Kip Thorne to imagine traversable wormholes created by holding the 'throat' of a Schwarzschild wormhole open with exotic matter (material that has negative mass/energy).

Traversability

Lorentzian traversable wormholes would allow travel from one part of the universe to another part of that same universe very quickly or would allow travel from one universe to another. The possibility of traversable wormholes in general relativity was first demonstrated by Kip Thorne and his graduate student Mike Morris in a 1988 paper; for this reason, the type of traversable wormhole they proposed, held open by a spherical shell of exotic matter, is referred to as a Morris-Thorne wormhole. Later, other types of traversable wormholes were discovered as allowable solutions to the equations of general relativity, including a variety analyzed in a 1989 paper by Matt Visser, in which a path through the wormhole can be made in which the traversing path does not pass through a region of exotic matter. However in the pure Gauss-Bonnet theory exotic matter is not needed in order for wormholes to exist- they can exist even with no matter.[2] A type held open by negative mass cosmic strings was put forth by Visser in collaboration with Cramer et al.,[3] in which it was proposed that such wormholes could have been naturally created in the early universe.

Wormholes connect two points in spacetime, which means that they would in principle allow travel in time, as well as in space. In 1988, Morris, Thorne and Yurtsever worked out explicitly how to convert a wormhole traversing space into one traversing time.[4] However, it has been said a time traversing wormhole cannot take a person back to before it was made[citation needed] but this is disputed.

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Faster-than-light travel

Special relativity only applies locally.[citation needed] Wormholes allow superluminal (faster-than-light) travel by ensuring that the speed of light is not exceeded locally at any time. While traveling through a wormhole, subluminal (slower-than-light) speeds are used. If two points are connected by a wormhole, the time taken to traverse it would be less than the time it would take a light beam to make the journey if it took a path through the space outside the wormhole. However, a light beam traveling through the wormhole would always beat the traveler. As an analogy, running around to the opposite side of a mountain at maximum speed may take longer than walking through a tunnel crossing it.

Time travel

A wormhole could allow time travel.[4] This could be accomplished by accelerating one end of the wormhole to a high velocity relative to the other, and then sometime later bringing it back; relativistic time dilation would result in the accelerated wormhole mouth aging less than the stationary one as seen by an external observer, similar to what is seen in the twin paradox. However, time connects differently through the wormhole than outside it, so that synchronized clocks at each mouth will remain synchronized to someone traveling through the wormhole itself, no matter how the mouths move around. This means that anything which entered the accelerated wormhole mouth would exit the stationary one at a point in time prior to its entry.

For example, consider two clocks at both mouths both showing the date as 2000. After being taken on a trip at relativistic velocities, the accelerated mouth is brought back to the same region as the stationary mouth with the accelerated mouth's clock reading 2005 while the stationary mouth's clock read 2010. A traveller who entered the accelerated mouth at this moment would exit the stationary mouth when its clock also read 2005, in the same region but now five years in the past. Such a configuration of wormholes would allow for a particle's world line to form a closed loop in spacetime, known as a closed timelike curve.

It is thought that it may not be possible to convert a wormhole into a time machine in this manner; some analyses using the semiclassical approach to incorporating quantum effects into general relativity indicate that a feedback loop of virtual particles would circulate through the wormhole with ever-increasing intensity, destroying it before any information could be passed through it, in keeping with the chronology protection conjecture. This has been called into question by the suggestion that radiation would disperse after traveling through the wormhole, therefore preventing infinite accumulation. The debate on this matter is described by Kip S. Thorne in the book Black Holes and Time Warps. There is also the Roman ring, which is a configuration of more than one wormhole. This ring seems to allow a closed time loop with stable wormholes when analyzed using semiclassical gravity, although without a full theory of quantum gravity it is uncertain whether the semiclassical approach is reliable in this case.

Metrics

Theories of wormhole metrics describe the spacetime geometry of a wormhole and serve as theoretical models for time travel. An example of a (traversable) wormhole metric is the following:

ds^2= - c^2 dt^2 + dl^2 + (k^2 + l^2)(d \theta^2 + \sin^2 \theta \, d\phi^2).

One type of non-traversable wormhole metric is the Schwarzschild solution:

ds^2= - c^2 \left(1 - \frac{2GM}{rc^2}\right)dt^2 + \frac{dr^2}{1 - \frac{2GM}{rc^2}} + r^2(d \theta^2 + \sin^2 \theta \, d\phi^2).

In fiction

Wormholes are features of science fiction as they allow interstellar (and sometimes interuniversal) travel within human timescales. It is common for the creators of a fictional universe to decide that faster-than-light travel is either impossible or that the technology does not yet exist, but to use wormholes as a means of allowing humans to travel long distances in short periods. Military science fiction (such as the Wing Commander games) often uses a "jump drive" to propel a spacecraft between two fixed "jump points" connecting stellar systems. Connecting systems in a network like this results in a fixed "terrain" with choke points that can be useful for constructing plots related to military campaigns. The Alderson points used by Larry Niven and Jerry Pournelle in The Mote in God's Eye and related novels are an example, although the mechanism does not seem to describe actual wormhole physics. David Weber has also used the device in the Honorverse and other books such as those based upon the Starfire universe. Naturally occurring wormholes form the basis for interstellar travel in Lois McMaster Bujold's Vorkosigan Saga. They are also used to create an Interstellar Commonwealth in Peter F. Hamilton's Commonwealth Saga. In Jack L. Chalker's The Rings of the Master series, interstellar class spaceships are capable of calculating complex equations and punching Wormholes in the fabric of the Universe in order to enable rapid travel.

The Massively Multiplayer Online Game EVE Online utilizes wormholes extensively as they are created in the use of the stargate technology which allows for interstellar travel in the game world.[5]

Wormholes also play pivotal roles in science fiction where faster-than-light travel is possible though limited, allowing connections between regions that would be otherwise unreachable within conventional timelines. Several examples appear in the Star Trek franchise, including the Bajoran wormhole in the Deep Space Nine series. In 1979's Star Trek: The Motion Picture the USS Enterprise was trapped in an artificial wormhole caused by an imbalance in the calibration of the ship's warp drive engines when it first achieved faster-than-light speed. In the Star Trek: Voyager series, the cybernetic species the Borg use what, in the Star Trek universe, are referred to as transwarp conduits, allowing ships to move nearly instantaneously to any part of the galaxy in which an exit apeture exists. Although these conduits are never described as "wormholes", they appear to share several traits in common with them.

The 1979 Disney film The Black Hole's plot centers around a massive black hole, although it makes virtually no use of then-current worm-hole physics, with only one rather desultory mention of an Einstein-Rosen bridge. A trip through the black hole turns theological, abandoning scientific rationale.

In Carl Sagan's novel Contact and subsequent 1997 film starring Jodie Foster and Matthew McConaughey, Foster's character Ellie travels 26 light years through a series of wormholes to the star Vega. The round trip, which to Ellie lasts 18 hours, passes by in a fraction of a second on Earth, making it appear she went nowhere. In her defense, Foster mentions an Einstein-Rosen bridge and tells how she was able to travel faster than light and time. Analysis of the situation by Kip Thorne, on the request of Sagan, is quoted by Thorne as being his original impetus for analyzing the physics of wormholes.

Wormholes play a major role in the television series Farscape, where they are the cause of John Crichton's presence in the far reaches of our galaxy and the focus of an arms race of different alien species attempting to obtain Crichton's perceived ability to control them. Crichton's brain was secretly implanted with knowledge of wormhole technology by one of the last members of an ancient alien species. Later, an alien interrogator discovers the existence of the hidden information and thus Crichton becomes embroiled in interstellar politics and warfare while being pursued by all sides (as they want the ability to use wormholes as weapons). Unable to directly access the information, Crichton is able to subconsciously foretell when and where wormholes will form and is able to safely travel through them (while all attempts by others are fatal). By the end of the series, he eventually works out some of the science and is able to create his own wormholes (and shows his pursuers the consequences of a wormhole weapon).

Wormholes are the basis for the Stargate franchise, where stargate devices create a stable artificial wormhole where matter is dematerialized, converted into energy, and is sent through to be rematerialized at the other side. A galactic system of stargates was built by aliens known as the Ancients or the Alterans, and later came to be used by other aliens who discovered them. In the inaugural film, a stargate was discovered on Earth in Egypt by an archeologist, which introduced humanity to the existence of inhabited worlds elsewhere. In the subsequent television series, humans explore the galaxy using the stargates (and must protect Earth from the hostile forces who now know a stargate is active on Earth).

In the science fiction series Sliders, a wormhole (or vortex, as it is usually called in the show) is used to travel between parallel worlds, and one is seen at least once or twice in every episode. In the pilot episode it was referred to as an "Einstein-Rosen-Podolsky bridge".

The central theme in the movie Donnie Darko revolves around Einstein-Rosen bridges.

In Command & Conquer 3 and in its expansion the Scrin faction (an alien lifeform with unknown origins from outer solar system) uses artificial wormholes for military purposes to convey infantry and vehicles behind enemy lines.

In the Invader Zim episode, "A Room with a Moose" Zim utilizes a wormhole to send his classmates into a parallel universe that consists entirely of a room with a large moose inside it.

In the episode titled "Wormhole" from the 2005 season of the long running American series Power Rangers, called Power Rangers SPD the SPD Rangers from the year 2025 travel back in time via a Wormhole to team up with the previous team of Power Rangers Dino Thunder from the year 2004, after their enemy Emperor Grumm goes through one.

In the video game "Supreme Commander" the UEF, Aeon Illuminate and Cybran Nation factions use "Quantum-gates" for long distance travel (noted in the Supreme Commander intro movie).

In the video game "Spore", the player can travel through various black holes, which act as wormholes for the player to go to its counterpart located usually on the other side of the galaxy; something that would take much longer to do by flying there manually.

In the second part of the episode "Acmegeddon" on the 2005 animated series Loonatics Unleashed, it was revealed that Zadavia's brother Optimatus had perfected wormhole technology on their home planet Freleng, and planned to use it to inavde and conquer other planets. Her open defiance led her to flee the planet for her life using a wormhole generator, and exiling herself on Acmetropolis. At the end of the episode she uses a handheld wormhole generator to send her borther to a cold and lonely asteroid.

In the movie Jumper, the "jumpers" are shown to open wormholes to move to any location they choose, instantly.

The 2007 game Metroid Prime 3: Corruption featured living meteors called "Leviathans" which could generate Wormholes to reach the furthest corners of the Universe, expediting their journeys to the selected planet of impact.

In the game Starlancer developed by Digital Anvil the player encounters several "Warp Gates" throughout missions. These gates appear to contain one end of a wormhole and are capable of opening the other end at a desired location of any distance (e.g In mission three the player is pulled through a warpgate near Neptune and comes out a few seconds later at Venus). About halfway through the game the player gains access to a "Warp Projector" which is a wormhole generator built into their fighter craft. Nearer to the end of the game various capital ships are also seen to implement warp projectors, most notably the ANS Yamato.

In the Red Dwarf episode Rimmerworld Rimmer's escape pod from the Simulant ship travels through a wormhole on an unchangeable course and lands on a planet with similar gravity to Earth. During the escape Kryten hypothesises that due to the time dilation a few hours passed on the current side would equate to centuries on the other; when the crew arrives on the planet they are apprehended and imprisoned by a humanoid race cloned from - and consisting entirely of - Rimmer, and upon reuniting with the original Rimmer hologram they find out he has been incarcerated for 557 years as his spawn were incapable of killing him.

See also

Notes

  1. ^ Coleman, Korte, Hermann Weyl's Raum - Zeit - Materie and a General Introduction to His Scientific Work, p. 199
  2. ^ gr-qc/0701152 (January 2007) `Mass without mass' from thin shells in Gauss-Bonnet gravity Elias Gravanis and Steven Willison
  3. ^ John G. Cramer, Robert L. Forward, Michael S. Morris, Matt Visser, Gregory Benford, and Geoffrey A. Landis, "Natural Wormholes as Gravitational Lenses," Phys. Rev. D51 (1995) 3117-3120
  4. ^ a b M. Morris, K. Thorne, and U. Yurtsever, Wormholes, Time Machines, and the Weak Energy Condition, Physical Review, 61, 13, September 1988, pp. 1446 - 1449
  5. ^ http://www.eveonline.com/background/jump/jump_03.asp

References

External links


Study guide

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Simple English


A wormhole is a shortcut through time and space. It is not known if wormholes exist in nature. Scientists believe that if wormholes existed they could not be made following any traditional scientific methods. In order to hold a wormhole open, a form of theoretical exotic matter would be needed. Otherwise the wormhole would simply disappear very quickly after its creation. If plotted on a 2-dimensional plane, the wormhole bends the plane, like folding a paper, so that the two ends would be touching. (as seen in the picture). The term wormhole was first used by John Wheeler, a theoretical physicist.


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